Wound dressing and method of treatment

ABSTRACT

Embodiments disclosed herein are directed to negative pressure treatment systems and wound dressing systems, apparatuses, and methods that may be used for the treatment of wounds. In particular, some embodiments are directed to improved wound dressings comprising a number of viewing portals that facilitate observation of wound tissue or healthy skin underlying the wound dressing. Some embodiments of the viewing portals are provided by forming through holes in internal dressing layers including absorbent material and transmission material, optionally by providing a plug material within the through holes, and by providing translucent or transparent cover layer and tissue contact layer materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/013,989, filed Jun. 18, 2014, titled “WOUND DRESSING AND METHODOF TREATMENT,” and U.S. Provisional Application Ser. No. 62/085,774,filed Dec. 1, 2014, titled “WOUND DRESSING AND METHOD OF TREATMENT,” theentireties of each of which are hereby incorporated by reference.

FIELD OF THE INVENTION

Embodiments described herein relate to apparatuses, systems, and methodsthe treatment of wounds, for example using dressings in combination withnegative pressure wound therapy.

SUMMARY OF THE INVENTION

Certain embodiments disclosed herein relate to improved wound dressingsthat exhibit enhanced visibility for underlying patient tissue. Suchdressings may have advantages over prior art dressings, through whichassessment of the condition of a tissue site underlying the dressing isdifficult or not possible. Also disclosed are improved methods of useand systems for use of the same, preferably in conjunction with negativepressure wound therapy.

In one embodiment, an apparatus for negative pressure wound therapycomprises:

-   -   a wound dressing comprising:    -   a material layer comprising one or more through holes extending        vertically through a thickness of the material layer; and    -   a transparent or translucent cover layer positioned above the        absorbent layer, the cover layer configured to form a negative        pressure chamber underneath the cover layer; and    -   a port configured to communicate negative pressure to the        negative pressure chamber;    -   wherein the one or more through holes in the material layer        permit viewing of tissue beneath the wound dressing through the        wound cover when the wound dressing is applied to a patient.

In some embodiments, the wound dressing comprises one or more lowerlayers beneath the material layer, wherein the through holes in thematerial layer permit viewing of tissue beneath the wound dressingthrough the wound cover and through the one or more lower layers whenthe wound dressing is applied to a patient. The one or more lower layersmay comprise one or more transparent or translucent layers. The one ormore lower layers may comprise a lower layer comprising one or morethrough holes extending vertically through a thickness of the lowerlayer. At least some of the vertically extending through holes in thelower layer may be positioned underneath at least some of the verticallyextending through holes in the material layer. The vertically extendingthrough holes in the lower layer may be smaller than the verticallyextending through holes in the material layer. The one or more lowerlayers may comprise a tissue contact layer and a transmission layer overthe tissue contact layer. The material layer may be an absorbent layer.

Some or all of the through holes in the material layer and in any lowerlayer may be circular in shape. Some or all of the through holes in thematerial layer and in any lower layer may be hexagonal in shape. Some orall of the through holes in the material layer and in any lower layermay be diamond-shaped. In some embodiments the apparatus may furthercomprise a filter in or below the port to retain wound exudateunderneath the cover layer. The apparatus may further comprise a fluidcollection canister for storage of fluids transported from the wounddressing. The port may be attached over a hole in the cover layer. Theapparatus may further comprise a conduit connected to the portconfigured to supply negative pressure to the wound dressing. Theapparatus may further comprise a source of negative pressure configuredto supply negative pressure to the wound dressing.

In some embodiments, the wound dressing may further comprise a plugmaterial positioned within at least some of the one or more throughholes. The plug material may prevent or minimize suction blistersforming in the tissue underneath the at least some of the one or morethrough holes. The plug material may comprise a soft, transparentmaterial. The plug material may comprise a soft, transparent, andhydrophobic material. The plug material may comprise silicone. In someembodiments, the one or more through holes can be configured to preventor minimize suction blisters to the tissue by having a limited diameter.The limited diameter can be less than or equal to approximately 10 mm.

In another embodiment, an apparatus for negative pressure woundcomprises:

-   -   a wound dressing comprising:    -   a transmission layer comprising one or more through holes        extending vertically through a thickness of the transmission        layer;    -   an absorbent layer comprising one or more through holes        extending vertically through a thickness of the absorbent layer;        and    -   a transparent or translucent cover layer positioned above the        absorbent layer, the cover layer configured to form a negative        pressure chamber underneath the cover layer; and    -   a port configured to communicate negative to pressure to the        negative pressure chamber;    -   wherein the one or more through holes in the transmission layer        are positioned at least partially below the one or more through        holes in the absorbent layer to permit viewing of tissue beneath        the wound dressing through the wound cover when the wound        dressing is applied to a patient.

In some embodiments, the transmission layer comprises a plurality ofhorizontally spaced apart through holes extending vertically through thethicknesss of the transmission layer, and the absorbent layer comprisesa plurality of horizontally spaced apart through holes extendingvertically through the thickness of the absorbent layer. The pluralityof horizontally spaced apart through holes in the transmission layer maybe distributed in a regularly spaced pattern across the transmissionlayer, and the plurality of horizontally spaced apart through holes inthe absorbent layer may be distributed in a regularly spaced patternacross the absorbent layer. The plurality of horizontally spaced apartthrough holes in the transmission layer may be spaced apart by 10 mm (orabout 10 mm) or less, and the plurality of horizontally spaced apartthrough holes in the absorbent layer may be spaced apart by 10 mm (orabout 10 mm) or less. The plurality of horizontally spaced apart throughholes in the transmission layer may be formed in a first pattern acrossan area of the transmission layer, and the plurality of horizontallyspaced apart through holes in the absorbent layer may be formed in asecond pattern across an area of the transmission layer.

In some embodiments, at least one through hole extending verticallythrough the thickness of the transmission layer is located below eachthrough hole extending vertically through the thickness of the absorbentlayer. Two or more through holes extending vertically through thethickness of the transmission layer may be located below each throughhole extending vertically through the thickness of the absorbent layer.The through hole(s) extending vertically through the thickness of theabsorbent layer may be larger in dimension than through hole(s)extending vertically through the thickness of the transmission layer.Some or all of the through holes in the transmission layer and/or theabsorbent layer may be circular in shape. Some or all of the throughholes in the transmission layer and/or the absorbent layer may behexagonal in shape. Some or all of the through holes in the transmissionlayer and/or the absorbent layer may be diamond-shaped. T

In some embodiments, the one or more through holes in the absorbentlayer can have a diameter of 10 mm (or about 10 mm) or less. The one ormore through holes in the transmission layer can have a diameter of 5 mm(or about 5 mm) or less. The one or more through holes in thetransmission layer can have a diameter of 1 mm (or about 1 mm) or less.

In some embodiments, the apparatus may further comprise a tissue contactlayer positioned below the transmission layer. The cover layer may beconfigured to seal around a perimeter thereof to the tissue contactlayer. The tissue contact may be is configured to seal directly to apatient's tissue. The transmission layer may comprise 3D fabric. Theabsorbent layer may comprise a non-woven material comprising a pluralityof superabsorbing particles. In some embodiments, the apparatus mayfurther comprise a fluid collection canister for storage of fluidstransported from the wound dressing.

In some embodiments, the apparatus may further comprise a filter in orbelow the port to retain wound exudate underneath the cover layer. Theport may be attached over a hole in the cover layer. In someembodiments, the apparatus may further comprise a conduit connected tothe port configured to supply negative pressure to the wound dressing.In some embodiments, the apparatus may further comprise a source ofnegative pressure configured to supply negative pressure to the wounddressing.

In some embodiments, the apparatus may further comprise a plug materialpositioned within at least some of the one or more through holes. Theplug material may prevent or minimize suction blisters forming in thetissue underneath the at least some of the one or more through holes.The plug material may comprise a soft, transparent material. The plugmaterial may comprise a soft, transparent, and hydrophobic material. Theplug material may comprise silicone.

In some embodiments, the one or more through holes can be configured toprevent or minimize suction blisters to the tissue by having a limiteddiameter. The limited diameter can be less than or equal toapproximately 10 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed aspects will hereinafter be described in conjunction withthe appended drawings, provided to illustrate and not to limit thedisclosed aspects, wherein like designations denote like elements.

FIG. 1 illustrates an embodiment of a wound treatment system;

FIGS. 2A-E illustrate the use and application of an embodiment of awound treatment system onto various wounds;

FIGS. 3A-3C illustrate an embodiment of a wound dressing configured forenhanced tissue visibility;

FIGS. 4A-4C illustrate another embodiment of a wound dressing configuredfor enhanced tissue visibility;

FIGS. 5A-5C illustrate another embodiment of a wound dressing configuredfor enhanced tissue visibility;

FIGS. 6A-6C illustrate various embodiments of a wound dressingconfigured for enhanced tissue visibility;

FIG. 7 illustrates another embodiment of a wound dressing configured forenhanced tissue visibility;

FIGS. 8A and 8B illustrate one embodiment of spacer layer material;

FIGS. 9A and 9B illustrate one embodiment of acquisition distributionlayer material;

FIGS. 10A and 10B illustrate one embodiment of absorbent layer material;and

FIG. 11 illustrates one embodiment of an adhesive spread on cover layermaterial.

FIGS. 12A-12E are photographic representations of various embodiments ofa wound dressing configured for enhanced tissue visibility through plugmaterial.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments disclosed herein relate to apparatuses and methods oftreating a wound with reduced pressure, including pump and wounddressing components and apparatuses. The apparatuses and componentscomprising the wound overlay and packing materials, if any, aresometimes collectively referred to herein as dressings.

It will be appreciated that throughout this specification reference ismade to a wound. It is to be understood that the term wound is to bebroadly construed and encompasses open and closed wounds in which skinis torn, cut or punctured or where trauma causes a contusion, or anyother superficial or other conditions or imperfections on the skin of apatient or otherwise that benefit from reduced pressure treatment. Awound is thus broadly defined as any damaged region of tissue wherefluid may or may not be produced. Examples of such wounds include, butare not limited to, abdominal wounds or other large or incisionalwounds, either as a result of surgery, trauma, sterniotomies,fasciotomies, or other conditions, dehisced wounds, acute wounds,chronic wounds, subacute and dehisced wounds, traumatic wounds, flapsand skin grafts, lacerations, abrasions, contusions, burns, diabeticulcers, pressure ulcers, stoma, surgical wounds, trauma and venousulcers or the like. Some embodiments of the dressings described hereinmay be used over a tissue site susceptible to form a wound or likely toform a wound, for example a tissue site over a bony prominencesusceptible to forming a pressure ulcer.

It will be understood that embodiments of the present disclosure aregenerally applicable to use in topical negative pressure (“TNP”) therapysystems. Briefly, negative pressure wound therapy assists in the closureand healing of many forms of “hard to heal” wounds by reducing tissueoedema; encouraging blood flow and granular tissue formation; removingexcess exudate and may reduce bacterial load (and thus infection risk).In addition, the therapy allows for less disturbance of a wound leadingto more rapid healing. TNP therapy systems may also assist on thehealing of surgically closed wounds by removing fluid and by helping tostabilize the tissue in the apposed position of closure. A furtherbeneficial use of TNP therapy can be found in grafts and flaps whereremoval of excess fluid is important and close proximity of the graft totissue is required in order to ensure tissue viability.

As is used herein, reduced or negative pressure levels, such as −X mmHg,represent pressure levels that are below standard atmospheric pressure,which corresponds to 760 mmHg (or 1 atm, 29.93 inHg, 101.325 kPa, 14.696psi, etc.). Accordingly, a negative pressure value of −X mmHg reflectsabsolute pressure that is X mmHg below 760 mmHg or, in other words, anabsolute pressure of (760−X) mmHg. In addition, negative pressure thatis “less” or “smaller” than X mmHg corresponds to pressure that iscloser to atmospheric pressure (e.g., −40 mmHg is less than −60 mmHg).Negative pressure that is “more” or “greater” than −X mmHg correspondsto pressure that is further from atmospheric pressure (e.g., −80 mmHg ismore than −60 mmHg).

The negative pressure range for some embodiments of the presentdisclosure can be approximately −80 mmHg, or between about −20 mmHg and−200 mmHg. Note that these pressures are relative to normal ambientatmospheric pressure. Thus, −200 mmHg would be about 560 mmHg inpractical terms. In some embodiments, the pressure range can be betweenabout −40 mmHg and −150 mmHg. Alternatively a pressure range of up to−75 mmHg, up to −80 mmHg or over −80 mmHg can be used. Also in otherembodiments a pressure range of below −75 mmHg can be used.Alternatively, a pressure range of over approximately −100 mmHg, or even150 mmHg, can be supplied by the negative pressure apparatus. In someembodiments of wound closure devices described here, increased woundcontraction can lead to increased tissue expansion in the surroundingwound tissue. This effect may be increased by varying the force appliedto the tissue, for example by varying the negative pressure applied tothe wound over time, possibly in conjunction with increased tensileforces applied to the wound via embodiments of the wound closuredevices. In some embodiments, negative pressure may be varied over timefor example using a sinusoidal wave, square wave, and/or insynchronization with one or more patient physiological indices (e.g.,heartbeat).

As used herein, the term “horizontal,” when referring to a wound,indicates a direction or plane generally parallel to the skinsurrounding the wound. The term “vertical,” when referring to a wound,generally refers to a direction extending perpendicular to thehorizontal plane. The terms “horizontal” and “vertical” may also be usedto describe the components of the wound treatment system, such as layersof the wound dressing. When describing these components, these termsshould not be construed to require that the structures or devicesnecessarily be placed into a wound in a certain orientation, though incertain embodiments, it may be preferable to do so.

I. Example Systems and Use

FIG. 1 illustrates an embodiment of a TNP wound treatment system 100comprising a wound dressing 110 in combination with a pump 150. Thewound dressing 110 can be any wound dressing embodiment disclosed hereinincluding without limitation dressing embodiment or have any combinationof features of any number of wound dressing embodiments disclosedherein. Here, the dressing 110 may be placed over a wound as describedpreviously, and a conduit 130 may then be connected to the port 120,although in some embodiments the dressing 101 may be provided with atleast a portion of the conduit 130 preattached to the port 120.Alternatively, in some embodiments the dressing 110 can be placed over atissue site likely to form a wound, such as a pressure site likely toform a pressure ulcer. Preferably, the dressing 110 is provided as asingle article with all wound dressing elements (including the port 120)pre-attached and integrated into a single unit. The wound dressing 110may then be connected, via the conduit 130, to a source of negativepressure such as the pump 150. The pump 150 can be miniaturized andportable, although larger conventional pumps may also be used with thedressing 110. In some embodiments, the pump 150 may be attached ormounted onto or adjacent the dressing 110. A connector 140 may also beprovided so as to permit the conduit 130 leading to the wound dressing110 to be disconnected from the pump, which may be useful for exampleduring dressing changes. Embodiments of the dressing of FIG. 1 arefurther described with respect to FIGS. 3A-11, which also provideadditional details on the specific internal components of the dressingembodiment depicted in FIG. 1.

In some embodiments, fluid may be transported from the dressing 110 andstored in a fluid collection canister (not shown). Some embodiments, maycall for fluid to be retained within the dressing such as within anabsorbent material. The absorbent material may further comprise asuperabsorbent polymer or a more conventional absorbent material such ascellulose.

FIGS. 2A-D illustrate the use of an embodiment of a TNP wound treatmentsystem being used to treat a wound site on a patient. FIG. 2A shows awound site 200 being cleaned and prepared for treatment. Here, thehealthy skin surrounding the wound site 200 is preferably cleaned andexcess hair removed or shaved. The wound site 200 may also be irrigatedwith sterile saline solution if necessary. Optionally, a skin protectantmay be applied to the skin surrounding the wound site 200. If necessary,a wound packing material, such as foam or gauze, may be placed in thewound site 200. This may be preferable if the wound site 200 is a deeperwound. In embodiments, the wound may be any type of wound describedherein this section or elsewhere in the specification.

FIG. 2B illustrates an incisional wound site 202 that may be irrigatedand prepared as the wound site 200 described in relation to FIG. 2A.Typical incisional wounds are created by a scalpel or other means duringsurgery to allow a clinician access to the underlying tissues andorgans. The incisional wound 202 may be closed, whereby the wound hasbeen closed by sutures 204 or other means such as an adhesive, or theincisional wound may be open, wherein the wound has not yet been closed.As described above, throughout this specification reference is made to awound and such a wound may be created by a variety of means includingvia incisional means. Thus, it will be understood by one skilled in theart, when the term “wound” is used in describing embodiments herein thissection and elsewhere in the specification, the term “wound” encompassesincisional wounds such as those described in FIG. 2B. Although notillustrated, the term “wound” also encompasses potential wound sites,such as bony prominences that may form a pressure ulcer.

After the skin surrounding the wound site 200 is dry, and with referencenow to FIG. 2C, the wound dressing 110 may be positioned and placed overthe wound site 200 or 202. Preferably, the wound dressing 110 is placedover and/or in contact with the wound site 200. In some embodiments, anadhesive layer is provided on the lower surface of the dressing 110,which may in some cases be protected by an optional release layer to beremoved prior to placement of the wound dressing 110 over the wound site200. Preferably, the dressing 110 is positioned such that the port 120is in a raised position with respect to the remainder of the dressing110 so as to avoid fluid pooling around the port. In some embodiments,the dressing 110 is positioned so that the port 120 is not directlyoverlying the wound, and is level with or at a higher point than thewound. To help ensure adequate sealing for negative pressure woundtherapy, the edges of the dressing 110 are preferably smoothed over toavoid creases or folds.

With reference now to FIG. 2D, the dressing 110 is connected to the pump150. The pump 150 is configured to apply negative pressure to the woundsite via the dressing 110, and typically through a conduit. In someembodiments, and as described above in FIG. 1, a connector may be usedto join the conduit from the dressing 110 to the pump 150. Upon theapplication of negative pressure with the pump 150, the dressing 110may, in some embodiments, partially collapse and present a wrinkledappearance as a result of the evacuation of some or all of the airunderneath the dressing 110. In some embodiments, the pump 150 may beconfigured to detect if any leaks are present in the dressing 110, suchas at the interface between the dressing 110 and the skin surroundingthe wound site 200. Should a leak be found, such leak is preferablyremedied prior to continuing treatment.

Turning to FIG. 2E, additional fixation strips 210 may also be attachedaround the edges of the dressing 110. Such fixation strips 210 may beadvantageous in some situations so as to provide additional sealingagainst the skin of the patient surrounding the wound site 200. Forexample, the fixation strips 210 may provide additional sealing for whena patient is more mobile. In some cases, the fixation strips 210 may beused prior to activation of the pump 150, particularly if the dressing110 is placed over a difficult to reach or contoured area.

Treatment of the wound site 200 preferably continues until the wound hasreached a desired level of healing. In some embodiments, it may bedesirable to replace the dressing 110 after a certain time period haselapsed, or if the dressing is full of wound fluids. During suchchanges, the pump 150 may be kept, with just the dressing 110 beingchanged.

II. Example Dressings

FIGS. 3A-C illustrate various views of a viewing portal wound dressing300 that can be used in a similar system to FIG. 1 to provide visibilityof underlying tissue according to an embodiment of the disclosure. Insome circumstances, it can be beneficial for a clinician to be able tovisually assess the quality of the tissue underlying the dressing 300.For example, a clinician can assess the progress of healing of woundtissue underlying the dressing 300 in some examples. Viewing portals 330in the dressing 300 permit viewing of tissue beneath the wound dressingthrough the wound cover when the wound dressing is applied to a patient,for example allowing a clinician to view the tissue underlying thedressing to determine whether the tissue is a wound site, healthytissue, or an infection, to name a few. In other examples, the dressing300 can be applied as a prophylactic measure to healthy or relativelyhealthy skin in an area that may form a wound and the clinician may wishto monitor changes in the underlying tissue to determine whether a woundis forming. By monitoring changes in the color of the underlying tissueor for signs of the dermis breaking down, a clinician can determinewhether further treatment is needed, such as debridement. For instance,the dressing 300 may be applied to a bony prominence possibly prone toforming a pressure ulcer. The dressing 300 can provide cushioning toprotect the bony prominence, and the blood perfusion resulting fromnegative pressure applied through the dressing 300 can providetherapeutic benefits including preventing, delaying, or mitigatingformation of pressure ulcers. The viewing portals 330 in the dressing300 can allow a clinician to determine whether a wound has formed in theunderlying tissue and/or determine an approximate area of an ulcer. Inother examples, the dressing 300 can be applied as a prophylacticmeasure to reddened or bruised tissue, to tissue on pressure points suchas the shoulder or buttocks of bedridden patients, or the like. Thematerial layers of the dressing 300 can serve to transmit negativepressure to the tissue site and also absorb any initial exudate fromformation of a wound. These are just a few circumstances in which aclinician may wish to monitor changes in tissue underlying a dressing300. The clinician can use viewing portals 330 through the internallayers of the dressing to monitor tissue characteristics and changes, asdiscussed in more detail below.

FIG. 3A illustrates a top view of the wound dressing 300, FIG. 3Billustrates a schematic cross-sectional view of the wound dressing 300,and FIG. 3C illustrates an exploded view of various layers of the wounddressing 300. The wound dressing 300 can be located over a wound site orpotentially wound-forming tissue site to be treated. The dressing 300may be placed so as to form a sealed cavity over the wound site. In someembodiments, the dressing 300 comprises a cover layer 345 attached to anoptional tissue contact layer 350, both of which are described ingreater detail below. These two layers 345, 350 are preferably joined orsealed together around a perimeter 305 so as to define an interior spaceor chamber. The cover layer 345 can be configured to form a negativepressure chamber underneath the cover layer. The interior space orchamber may comprise additional structures that may be adapted todistribute or transmit negative pressure, store wound exudate and otherfluids removed from the wound, and other functions which will beexplained in greater detail below. Examples of such structures,described below, include a transmission layer 310 and/or an absorbentlayer 320.

The various layers used to form the wound dressing 300 or other wounddressings described in this specification may have any of a number ofperimeter shapes when viewed from above, as in FIG. 3A. For example, thelayers may have a rectangular, square, elongated, elliptical, circularor other shapes. In some embodiments, each of the layers has the same orsimilar shape, though they may be of different sizes (as shown in FIG.3C). FIG. 3A illustrates layers that have a rectangular shape with alength and a width extending within a horizontal plane. FIG. 3Billustrates that each of the layers may have a vertical thicknessperpendicular to the horizontal dimensions of the layers.

As illustrated in FIGS. 3A-C, a lower surface of the wound dressing 300may be provided with an optional tissue contact layer 350. The tissuecontact layer 350 can for example be a polyurethane layer orpolyethylene layer or other flexible layer which is perforated, forexample via a hot pin process, laser ablation process, ultrasoundprocess or in some other way or otherwise made permeable to liquid andgas. The tissue contact layer 350 has a lower surface and an uppersurface. As shown in FIG. 3B, perforations 360 may be provided in thetissue contact layer 350, preferably comprising through holes in thetissue contact layer 350 which enable fluid to flow through the layer350. The tissue contact layer 350 can help prevent tissue ingrowth intothe other material of the wound dressing. Preferably, the perforations360 are small enough to meet this requirement while still allowing fluidto flow therethrough. For example, perforations 360 formed as slits orholes having a size ranging from approximately 0.025 mm to approximately1.2 mm, for example 1 mm (or about 1 mm) are considered small enough tohelp prevent tissue ingrowth into the wound dressing while allowingwound exudate to flow into the dressing. In some configurations, thetissue contact layer 350 may help maintain the integrity of the entiredressing 300 while also creating an air tight seal around the internallayers in order to maintain negative pressure at the wound.

Some embodiments of the tissue contact layer 350 may also act as acarrier for an optional lower and/or upper adhesive layer (not shown).For example, a lower pressure sensitive adhesive may be provided on thelower surface of the tissue contact layer 350 whilst an upper pressuresensitive adhesive layer may be provided on the upper surface of thetissue contact layer 350. In some embodiments a pressure sensitiveadhesive, which may be a silicone, hot melt, hydrocolloid or acrylicbased adhesive or other such adhesives, may be formed on both sides oroptionally on a selected one side of the tissue contact layer. Incertain embodiments, the upper adhesive layer may comprise an acrylicpressure sensitive adhesive, and the lower adhesive layer may comprise asilicone pressure sensitive adhesive. In other embodiments the tissuecontact layer 350 may not be provided with adhesive. In someembodiments, the tissue contact layer 350 may be transparent ortranslucent. The film layer of the tissue contact layer 350 may define aperimeter with a rectangular or a square shape. A release layer (notillustrated) may be removably attached to the underside of the tissuecontact layer 350, for example covering the lower adhesive layer, andmay be peeled off using flaps. Some embodiments of the release layer mayhave a plurality of flaps extending along the length of the layer. Insome embodiments, the tissue contact layer 350 may comprise perforatedpolyurethane film. The lower surface of the film may be provided with asilicone pressure sensitive adhesive and the upper surface may beprovided with an acrylic pressure sensitive adhesive, which may help thedressing maintain its integrity. In some embodiments, a polyurethanefilm layer may be provided with an adhesive layer on both its uppersurface and lower surface, and all three layers (the upper adhesivelayer, the film layer, and the lower adhesive layer) may be perforatedtogether.

An optional layer of porous material can be located above the tissuecontact layer 350. This porous layer, or transmission layer 320, allowstransmission of fluid including liquid and gas away from a wound siteinto upper layer(s) of the wound dressing 300. In particular, thetransmission layer 320 preferably ensures that an open air channel canbe maintained to communicate negative pressure over the wound area evenwhen the overlying absorbent layer 310 has absorbed substantial amountsof exudates. The transmission layer 320 should preferably remain openunder the typical pressures that will be applied during negativepressure wound therapy as described above, so that the whole wound sitesees an equalized negative pressure.

Some embodiments of the transmission layer 320 may be formed of amaterial having a three dimensional structure. For example, a knitted orwoven spacer fabric (for example Baltex 7970 weft knitted polyester) ora non-woven fabric can be used. In some embodiments, the transmissionlayer 320 can have a 3D polyester spacer fabric layer. This layer canhave a top layer which is a 84/144 textured polyester, and a bottomlayer which can be a 100 denier flat polyester and a third layer formedsandwiched between these two layers which is a region defined by aknitted polyester viscose, cellulose or the like monofilament fiber. Inuse, this differential between filament counts in the spaced apartlayers tends to draw liquid away from the wound bed and into a centralregion of the dressing 300 where the absorbent layer 310 helps lock theliquid away or itself wicks the liquid onwards towards the cover layer345 where it can be transpired. Other materials can be utilized, andexamples of such materials are described in U.S. Patent Pub. No.2011/0282309, which are hereby incorporated by reference and made partof this disclosure.

Some embodiments of the transmission layer 320 may additionally oralternatively comprise a wicking or acquisition distribution material(ADL) to horizontally wick fluid such as wound exudate as it is absorbedupward through the layers of the dressing 300. Lateral wicking of fluidmay allow maximum distribution of the fluid through the absorbent layer330 and may enable the absorbent layer 310 to reach its full holdingcapacity. This may advantageously increase moisture vapor permeation andefficient delivery of negative pressure to the wound site. Someembodiments of the transmission layer 320 may comprise viscose,polyester, polypropylene, cellulose, or a combination of some or all ofthese, and the material may be needle-punched. Some embodiments of thetransmission layer 320 may comprise polyethylene in the range of 40-150grams per square meter (gsm).

Further details of example suitable materials for a transmission layer320 are discussed below with respect to FIGS. 8A-9B.

A layer 310 of absorbent material may be provided above the transmissionlayer 320. The absorbent material, which can comprise a foam ornon-woven natural or synthetic material, and which may optionallycomprise a super-absorbent material, forms a reservoir for fluid,particularly liquid, removed from the wound site. In some embodiments,the absorbent layer 310 may also aid in drawing fluids towards the coverlayer 345. The absorbent layer 310 can be manufactured from ALLEVYN™foam, Freudenberg 114-224-4 and/or Chem-Posite™ 11C-450, or any othersuitable material. Some embodiments of the absorbent layer can beconstructed from hydrophilic foam, for example a hydrophilicpolyurethane prepolymer such as HYPOL™. In some embodiments, theabsorbent layer 310 can be a layer of non-woven cellulose fibers havingsuper-absorbent material in the form of dry particles dispersedthroughout. Use of the cellulose fibers introduces fast wicking elementswhich help quickly and evenly distribute liquid taken up by thedressing. The juxtaposition of multiple strand-like fibers leads tostrong capillary action in the fibrous pad which helps distributeliquid.

For example, some embodiments of the absorbent layer 310 may comprise alayered construction of an upper layer of non-woven cellulose fibers,superabsorbent particles (SAP), and a lower layer of cellulose fiberswith 40-80% SAP. In some embodiments, the absorbent layer 310 may be anair-laid material. Heat fusible fibers can optionally be used to assistin holding the structure of the pad together. Some embodiments maycombine cellulose fibers and air-laid materials, and may furthercomprise up to 60% SAP. Some embodiments may comprise 60% SAP and 40%cellulose. Other embodiments of the absorbent layer may comprise between60% and 90% (or between about 60% and about 90%) cellulose matrix andbetween 10% and 40% (or between about 10% and about 40%) superabsorbentparticles. For example, the absorbent layer 310 may have about 20%superabsorbent material and about 80% cellulose fibers. It will beappreciated that rather than using super-absorbing particles or inaddition to such use, super-absorbing fibers can be utilized accordingto some embodiments of the present invention. An example of a suitablematerial is the Product Chem-Posite™ 11 C available from EmergingTechnologies Inc (ETi) in the USA.

Super-absorber particles/fibers can be, for example, sodium polyacrylateor carbomethoxycellulose materials or the like or any material capableof absorbing many times its own weight in liquid. In some embodiments,the material can absorb more than five times its own weight of 0.9% W/Wsaline, etc. In some embodiments, the material can absorb more than 15times its own weight of 0.9% W/W saline, etc. In some embodiments, thematerial is capable of absorbing more than 20 times its own weight of0.9% W/W saline, etc. Preferably, the material is capable of absorbingmore than 30 times its own weight of 0.9% W/W saline, etc. The absorbentlayer 310 can have one or more through holes 355 located so as tounderlie the suction port 335.

Further details of example suitable absorbent materials are discussedbelow with respect to FIGS. 10A-10B.

As illustrated in FIGS. 3A and 3C, the absorbent layer 310 may include anumber of through holes 315 and the transmission layer 320 can includean additional number of through holes 325. In some embodiments, thethrough holes 315 in the absorbent layer 310 and the through holes 325in the transmission layer 320 can be aligned to form viewing portals 330through the internal layers of the dressing 300. Due to the transparencyor translucency of the cover layer 345 and tissue contact layer 350, theviewing portals 330 can permit viewing of tissue beneath the wounddressing through the wound cover when the wound dressing is applied to apatient, for example for assessment of characteristics of and changes intissue underlying the dressing 300. In some embodiments, the pattern ofthe viewing portals 330 can aid a clinician in assessing the progress ofhealing of a wound underlying the dressing 300 by identifying locationsat which new healthy skin has formed. In other embodiments, the patternof the viewing portals 330 can aid a clinician in assessing theformation and area of a wound forming under the dressing 300, such as adiabetic ulcer or a pressure ulcer. In some embodiments, through holes325 in the transmission layer 320 may be approximately 2 mm in diameterand may be aligned with smaller holes or perforations in the tissuecontact layer 350. As discussed above, perforations 360 may be formed inthe tissue contact layer, and may be approximately 1 mm in diameter insome embodiments.

In some embodiments, some or all of through holes 315, 325 may comprise(that is, be plugged or filled using) a plug material, for example asoft, transparent and optionally hydrophobic material (e.g. silicone).Positioning such plug material within through holes 315, 325 canbeneficially reduce the risk of underlying skin or tissue being suckedinto voids in the dressing when the dressing is under negative pressure.Accordingly, in some examples the through holes 325 that are closest tothe wound site may be filled with plug material while the through holes315 further from the wound site may not be filled. Alternatively, thethrough holes 315 further from the wound site may be filled, and thethrough holes 325 closer to the wound site may not be filled with plugmaterial. The plug material can additionally provide the benefit ofpreventing lateral swelling of super absorbent particles in theabsorbent layer 310, which can cause the particles to spill out of theabsorbent layer 310 material at the cut edges, thereby filling (at leastpartially) the through holes 315, 325. Accordingly, in some examples atleast the through holes 315 in the absorbent layer may be filled withplug material. In one embodiment, an absorbent layer and an underlyingtransmission layer can have through holes that are aligned orsubstantially aligned, such that there is some visibility to theunderlying patient tissue. The through holes in the absorbent layer canbe filled with plug material, while the through holes in thetransmission layer positioned between the absorbent layer and the woundsite are not filled with plug material. Such a configuration can providefor better transmission of negative pressure to tissue underlying theplugged through holes compared to embodiments which provide plugmaterial in a material layer positioned adjacent to the wound site.

The transparency of the plug material provides visibility through to thewound bed. As a result of the hydrophobic nature of some embodiments ofthe plug material, the viewing portals 330 will remain transparentthroughout wear time as colored wound exudate and other substancesshould not be drawn into the plug material because it is hydrophobic.Some examples of the plug material are not absorbent so as to not fillwith exudate. In some embodiments, larger through holes can be providedin dressing embodiments using the plug material within through holescompared to dressing embodiments without plug material, for example dueto removal of size constraints for preventing patient tissue from beingdrawn into the holes. In some embodiments, when plugs are provided inthrough holes 315 of the absorbent layer 310 and optionally in thethrough holes 325 of the transmission layer 310, the through holes 325of the transmission layer 320 may be the same shape and dimension as thethrough holes 315. In other embodiments, when plugs are provided inthrough holes 315 of the absorbent layer 310, no transmission layer 310is provided.

The through holes 315 in the absorbent layer 310 may form a repeatingpattern across the area of the absorbent layer 310 with the exception ofthe area of the absorbent layer 310 including the through hole 355 forthe port 335. Here the repeating pattern is illustrated as a grid orarray of through holes 315 though in other embodiments other patternscan be used. In some embodiments, the through holes 315 in the absorbentlayer 310 and the through holes 325 in the transmission layer 320 may bespaced apart by 10 mm (or about 10 mm) or less. The through hole 355underlying the port 335 is illustrated as being separate from therepeating pattern of through holes 315 and larger than the through holes315, however in some embodiments the repeating pattern of through holes315 can continue across the entire area (or substantially all of thearea) of the absorbent layer 310 and the port can be placed over aselected one of the through holes in the array, or over a selected groupof adjacent through holes in the array. In the illustrated embodiment,the transmission layer 320 has no through holes underlying the throughhole 355 in the absorbent layer 310 over which the port 335 is applied.However, in other embodiments the pattern of through holes 325 in thetransmission layer 320 may continue under the through hole 355 in theabsorbent layer 310.

The through holes 315, 325 can be cut or formed in some embodiments bypunching, die cutting, or laser cutting the sheet materials used to formthe absorbent layer 310 and the transmission layer 320. However, thecreation of apertures, for example by hole-punching, has thedisadvantages of resulting in the generation of waste and also themechanical weakening of the material. By forming through slits in amaterial, these slits being capable of expanding to form apertures onextension of the material, increased visibility of the wound can beachieved without significant material waste. In this manner, it is alsopossible to achieve extension of the slit to form a circular holewithout mechanically weakening the material. Examples of such latticecutting techniques are disclosed in International Patent Publication No.PCT/US2007/079529, filed Sep. 26, 2007, titled “LATTICE DRESSING,” theentirety of which is hereby incorporated by reference. In someembodiments, for example embodiments in which the through holes 315 inthe absorbent layer 310 and the through holes 325 transmission layer 325are different sizes or are arranged in different patterns, the absorbentlayer 310 and transmission layer 325 can be cut separately from oneanother by any of the previously described hole-forming processes. Insome embodiments, the absorbent layer 310 and transmission layer 320 canbe stacked and the through holes 315, 325 cut through the stacked layers310, 325 at the same time by any of the previously describedhole-forming processes. In some embodiments separate plug materialportions can be provided to the through holes in various layers (here,absorbent layer 310 and transmission layer 320), for example as theholes are punched or cut in the layer. In some embodiments, the layersmay be stacked and hole punched or cut together and accordingly a singleportion of plug material can be provided extending through the holes315, 325 of multiple layers.

Although the through holes 315 in the absorbent layer 310 and thethrough holes 325 in the transmission layer 320 are depicted as beingcentered and aligned one-to-one, other alignments can be used in otherembodiments. For example, multiple smaller through holes 325 in thetransmission layer 320 can be aligned with larger through hole 315 inthe absorbent layer 310. Further, although the through holes 315 in theabsorbent layer 310 are depicted as being larger than the through holes325 in the transmission layer 320, in other embodiments the throughholes 315, 325 may be substantially equal sizes or the through holes 325in the transmission layer may be larger than the through holes 315 inthe absorbent layer 310. In some embodiments, non-woven materials mayrequire relatively larger holes (for example approximately 2 mm orlarger) than woven materials in order for the holes to remain open undernegative pressure. Depending on the amount of negative pressure appliedto the dressing 300, the through holes in the layer closest to thepatient tissue may be limited to a maximum diameter in order to preventthe formation of suction blisters by tissue pulled into the throughholes. In some embodiments, the through holes 325 in the transmissionlayer 320 may have a diameter of approximately 1 mm or less to preventthe underlying tissue from being pulled into the through holes 325 whennegative pressure is applied to the dressing 300, thereby preventingdamage to the tissue and/or discomfort to the patient. In otherembodiments, the through holes 325 may have a diameter of approximately10 mm or less. The through holes 315 in the absorbent layer 310 can havea diameter of approximately 2 mm to approximately 10 mm in someembodiments. Although through holes 315, 325 are illustrated as beinggenerally circular in shape, this is for purposes of illustration andother shapes can be used for through holes 315, 325 in other embodimentssuch as elliptical, square, rectangular, triangular, and hexagonal, toname a few.

In some embodiments, the through holes in one or both of the absorbentlayer and transmission layer 320 may be susceptible to closing undernegative pressure. Adhesive can be applied to the upper surface of thetissue contact layer 350 in some embodiments, and by contacting thetransmission layer 320 such adhesive can assist in maintaining theopenness of the through holes 325 in the transmission layer 320.Similarly, adhesive can be applied to the lower surface of the coverlayer 345 in some embodiments, and by contacting the absorbent layer 310such adhesive can assist in maintaining the openness of the throughholes 315 in the absorbent layer 310. Adhesive can be applied betweenthe absorbent layer 310 and the transmission layer 320 in someembodiments to assist in maintaining the openness of through holes 315,325 in both layers. For example, in some embodiments the adhesive layerbetween the absorbent layer 310 and the transmission layer 320 maycomprise an adhesive web or net. In other embodiments, the adhesivelayer may comprise adhesive tape. Yet other embodiments may employ a hotmelt adhesive a hot melt adhesive such as ethylene vinyl acetate (EVA).For example, EVA powder may be sprinkled over one or both of the layers310, 320, which may then be heat bonded. Preferred embodiments of theadhesive layer are hydrophilic so as not to affect the transport ofwater and/or water-based solutions between the absorbent layer 310 andthe transmission layer 320.

The absorbent layer 310 may be of a greater area than the transmissionlayer 320 in some embodiments, such that the absorbent layer 310overlaps two or more edges of the transmission layer 320, therebyensuring that the transmission layer does not contact the cover layer345. This can provide an outer channel of the absorbent layer that is indirect contact with the tissue contact layer 350 that aids more rapidabsorption of exudates to the absorbent layer. Furthermore, such anouter channel can ensure that no liquid is able to pool around thecircumference of the wound cavity, which may otherwise seep through theseal around the perimeter of the dressing leading to the formation ofleaks.

The cover layer 345 is preferably gas impermeable, but moisture vaporpermeable, and can extend across the width of the wound dressing 300.The cover layer 345, which may for example be a polyurethane film havinga pressure sensitive adhesive on one side, is impermeable to gas andthis layer thus operates to cover the wound and to seal a wound cavityover which the wound dressing is placed. In this way an effectivechamber is made between the cover layer 345 and a wound site where anegative pressure can be established. The cover layer 345 is preferablysealed to the tissue contact layer 350 in a border region 305 around thecircumference of the dressing, ensuring that no air is drawn in throughthe border area, for example via adhesive or welding techniques. Thecover layer 345 protects the wound or underlying tissue from externalbacterial contamination (bacterial barrier) and allows liquid from woundexudates to be transferred through the layer and evaporated from thefilm outer surface. The cover layer 345 preferably comprises two layers;a polyurethane film and an adhesive pattern spread onto the film. Someembodiments may employ a polyurethane film (for example, ElastollanSP9109) or any other suitable material. For example, certain embodimentsmay comprise translucent or transparent 30 gsm EU33 film. An example ofa cover contact layer adhesive spread is illustrated in FIG. 11 anddiscussed in more detail below. The polyurethane film is preferablymoisture vapor permeable and may be manufactured from a material thathas an increased water transmission rate when wet.

An orifice 365 is preferably provided in the cover layer 345 to allow anegative pressure to be applied to the dressing 300. A suction port 335is preferably attached or sealed to the top of the cover layer 345 overthe orifice 365 made or formed into the cover layer 345 to communicatenegative pressure through the orifice 365. A length of tubing 340 may becoupled at a first end to the suction port 335 and at a second end to apump unit (not shown) to allow transmission of negative pressure to thedressing 300 and, in some embodiments, to allow fluids to be pumped outof the dressing 300. The port 335 may be adhered and sealed to the coverlayer 345 using an adhesive such as an acrylic, cyanoacrylate, epoxy, UVcurable or hot melt adhesive. The illustrated embodiment of the port 335can be formed from a soft polymer, for example a polyethylene, apolyvinyl chloride, a silicone or polyurethane having a hardness of 30to 90 on the Shore A scale. However, the illustrated port 335 isintended to provide one example of a port suitable for use with thewound dressing 300 and not to limit the type of port usable with thedressing 300. In some embodiments, the port 335 may be made from a softor conformable material, for example using the embodiments described inInternational Patent Application No. PCT/M2013/001469, filed May 22,2013, titled “APPARATUSES AND METHODS FOR NEGATIVE PRESSURE WOUNDTHERAPY,” the entirety of which is hereby incorporated by reference.

Preferably the absorbent layer 310 includes at least one through hole355 located so as to underlie the port 335. The through hole 355, whileillustrated here as being larger than the hole through the cover layer345, may in some embodiments be bigger or smaller than the hole 365 incover layer 345. It will be appreciated that multiple openings couldalternatively be utilized. Additionally should more than one port beutilized according to certain embodiments of the present disclosure oneor multiple openings may be made in the absorbent layer 310 and thecover layer 345 in registration with each respective port. Although notessential to certain embodiments of the present disclosure the use ofthrough holes in a super-absorbent material forming the absorbent layer320 may provide a fluid flow pathway which remains unblocked inparticular when the absorbent layer 310 is near saturation.

Accordingly, the port 335 is in direct fluid communication with thetransmission layer 320 through orifice 365 and through hole 355. Thisallows the negative pressure applied to the port 335 to be communicatedto the transmission layer 320 without passing through the absorbentlayer 310, ensuring that the negative pressure applied to the wound siteis not inhibited by the absorbent layer 310 as it absorbs woundexudates. In use, for example when negative pressure is applied to thedressing 300, a wound facing portion of the port 335 may thus come intocontact with the transmission layer 320, which can thus aid intransmitting negative pressure to the wound site even when the absorbentlayer 310 is filled with wound fluids. Some embodiments may have thecover layer 345 be at least partly adhered to the transmission layer320. In some embodiments, the aperture 355 in the absorbent layer 310 isat least 1-2 mm larger than the diameter of the wound facing portion ofthe port 335. In other embodiments the aperture 355 in the absorbentlayer 310 is smaller than the diameter of the wound facing portion ofthe port 335. In other embodiments, no aperture may be provided in theabsorbent layer 310, or alternatively a plurality of aperturesunderlying the orifice 365 may be provided.

A filter element that is impermeable to liquids, but permeable to gasescan be provided in or below the port 335 to act as a liquid barrierbetween the dressing 300 and the conduit 340 in some embodiments toensure that no liquids are able to escape from the wound dressing 300.The filter element may also function as a bacterial barrier. The poresize can be approximately 0.2 μm. Suitable materials for the filtermaterial of the filter element include 0.2 micron Gore™ expanded PTFEfrom the MMT range, PALL Versapore™ 200R, and Donaldson™ TX6628. Largerpore sizes can also be used but these may require a secondary filterlayer to ensure full bioburden containment. As wound fluid containslipids it is preferable, though not essential, to use an oleophobicfilter membrane for example 1.0 micron MMT-332 prior to 0.2 micronMMT-323. This prevents the lipids from blocking the hydrophobic filter.The filter element can be attached or sealed to the port 335 and/or thecover layer 345 over the orifice 365. For example, the filter elementmay be molded into the port 335, or may be adhered to both the top ofthe cover layer 345 and bottom of the port 335 using an adhesive suchas, but not limited to, a UV cured adhesive.

In particular for embodiments with a single port 335, it may bepreferable for the port 335 to be located in an off-center position asillustrated in FIGS. 3A-C and in FIG. 1. Such a location may permit thedressing 300 to be positioned onto a patient such that the port 335 israised in relation to the remainder of the dressing 2100. So positioned,the port 335 may be less likely to come into contact with wound fluidsthat could prematurely occlude the port 335 so as to impair thetransmission of negative pressure to the wound site.

Some embodiments may be manufactured without the port 335 and mayinclude at least one area for attaching a port. For example, the portmay simply be an opening in the cover layer 345 for attaching a separateport member, and the opening may be preformed in the cover layer 345 orformed by a clinician by cutting, puncturing, or tearing the cover layer345.

In some embodiments, the tissue contact layer 350 may be flat and thecover layer 345 may be contoured over the inner layers of the dressing300. The absorbent layer 310 may be about 1.5 times thicker than thetransmission layer 320 in some embodiments.

FIGS. 4A-4C illustrate another embodiment of a wound dressing 400configured for enhanced tissue visibility. FIG. 4A illustrates a topview of the wound dressing 400, FIG. 4B illustrates a cross-sectionalview of the wound dressing 400, and FIG. 4C illustrates an exploded viewof various layers of the wound dressing 400. The wound dressing 400 canbe located over a wound site or potentially wound-forming tissue site tobe treated as described above. In some embodiments, the dressing 400comprises a cover layer 445 attached to a tissue contact layer 450, forexample any of the cover layer or tissue contact layer embodimentsdescribed above or below. These two layers 445, 450 can be joined orsealed together around a perimeter 405 so as to define an interior spaceor chamber in which therapeutic negative pressure can exist. Thisinterior space or chamber may include absorbent layer 410 andtransmission layer 420, which can be any of the absorbent materials ortransmission materials described above or below. A port 435 and conduit440 can be attached to the dressing 400 overlying an orifice 465 in thecover layer 445 and a through hole 455 in the absorbent layer 410 asdescribed above with respect to FIGS. 3A-3C for transmission of negativepressure from a pump to the dressing 400.

The absorbent layer 410 includes a number of through holes 415 arrangedin a repeating pattern. The transmission layer 320 includes anadditional number of through holes 425 of substantially the same size asthe through holes 415 in the absorbent layer 410 and arranged in asimilar repeating pattern. In some embodiments, the through holes 415 inthe absorbent layer 410 and the through holes 425 in the transmissionlayer 420 can be aligned or substantially aligned to form viewingportals 430 through the internal layers of the dressing 400. Asdescribed above, some or all of the through holes 415, 425 may comprisea plug material. As described above, due to the transparency ortranslucency of the cover layer 445 and tissue contact layer 450, theviewing portals 430 can permit viewing of tissue beneath the wounddressing through the wound cover when the wound dressing is applied to apatient, for example enabling a clinician to assess characteristics ofand changes in tissue underlying the dressing 400. In the illustratedembodiment, the transmission layer 420 has no through holes underlyingthe through hole 455 in the absorbent layer 410 over which the port 435is applied. However, in other embodiments the pattern of through holes425 in the transmission layer 420 may continue under the through hole455 in the absorbent layer 410.

FIGS. 5A-5C illustrate another embodiment of a wound dressing 500configured for enhanced tissue visibility. FIG. 5A illustrates a topview of the wound dressing 500, FIG. 5B illustrates a cross-sectionalview of the wound dressing 500, and FIG. 5C illustrates an exploded viewof various layers of the wound dressing 500. The wound dressing 500 canbe located over a wound site or potentially wound-forming tissue site tobe treated as described above. In some embodiments, the dressing 500comprises a cover layer 545 attached to a tissue contact layer 550, forexample any of the cover layer or tissue contact layer embodimentsdescribed above or below. These two layers 545, 550 can be joined orsealed together around a perimeter 505 so as to define an interior spaceor chamber in which therapeutic negative pressure can exist. Thisinterior space or chamber may include a single material layer 510, whichcan be any of the absorbent materials or transmission materialsdescribed above or below. A port 535 and conduit 540 can be attached tothe dressing 500 overlying the material layer 510 as described abovewith respect to FIGS. 3A-3C for transmission of negative pressure from apump to the dressing 500.

The material layer 510 can include a number of through holes 515 formingviewing portals 530 through the dressing. As described above, some orall of the through holes 515 may comprise a plug material. As describedabove, due to the transparency or translucency of the cover layer 545and tissue contact layer 550, the viewing portals 530 can permit viewingof tissue beneath the wound dressing through the wound cover when thewound dressing is applied to a patient, for example enabling a clinicianto assess characteristics of and changes in tissue underlying thedressing 500. The through holes 515 can be arranged in a repeatingpattern, here illustrated as hexagonal through holes 515 forming ahoneycomb pattern, across substantially all of the area of the materiallayer 510. The pattern can be discontinued in some embodiments in anarea underlying the port 535 so that the underlying tissue contact layer550 does not come into contact with and occlude the port 535 whennegative pressure is applied to the dressing 500.

FIGS. 6A-6C illustrate various embodiments of a wound dressingconfigured for enhanced tissue visibility. FIG. 6A illustrates a topview of the wound dressing 600A showing the perimeter 605 of a coverlayer and tissue contact layer, a material layer 610 below the coverlayer, and a pattern of through holes 615 in the material layer. Thethrough holes 615 are illustrated in FIG. 6A as being a single line ofsix substantially equally sized holes. FIG. 6B illustrates a top view ofanother embodiment of the wound dressing 600B showing the perimeter 605of a cover layer and backing layer, the material layer 610 below thecover layer, and a second embodiment of the pattern of through holes 615in the material layer. The through holes 615 are illustrated in FIG. 6Bas being three rows of six substantially equally sized holes. FIG. 6Cillustrates a top view of another embodiment of the wound dressing 600Cshowing the perimeter 605 of a cover layer and backing layer, a materiallayer 610 below the cover layer, and a pattern of through holes 615 inthe material layer. The through holes 615 are illustrated in FIG. 6C asbeing a circle of substantially equally sized holes positioned around acenter hole.

In some embodiments, a port can be placed over any of the holes in thepatterns illustrated in FIGS. 6A-6C. Though not illustrated, throughholes in a layer underneath the illustrated material layer 610 may besmaller than the through holes 615 in the material layer 610. Viewingportals can be formed through the dressing by aligning at least aportion of one or more holes in a lower layer with one of the throughholes 615 in the material layer 610. As described above, some or all ofthe through holes 615 may comprise a plug material.

FIG. 7 illustrates a top view of another embodiment of a wound dressing700 configured for enhanced tissue visibility. The wound dressing 700can be located over a wound site or potentially wound-forming tissuesite to be treated as described above. In some embodiments, the dressing700 comprises a cover layer attached to a tissue contact layer, forexample any of the cover layer or tissue contact layer embodimentsdescribed above or below, joined or sealed together around a perimeter705 so as to define an interior space or chamber in which therapeuticnegative pressure can exist. This interior space or chamber may includean absorbent layer 710 and a transmission layer positioned beneath theabsorbent layer, which can be any of the absorbent materials ortransmission materials described above or below. A port 735 and conduit740 can be attached to the dressing 700 overlying one of the throughholes 715 in the absorbent layer 710 for transmission of negativepressure from a pump to the dressing 700.

The absorbent layer 710 includes a number of through holes 715 arrangedin a pattern including three rows of seven substantially equally sizedholes 715. The transmission layer includes an additional number ofthrough holes 725 of a substantially smaller size than the through holes715 in the absorbent layer 710. The through holes 725 in thetransmission layer are arranged in a repeating pattern. When thetransmission layer and absorbent layer 710 are aligned under the coverlayer, multiple through holes 725 in the transmission layer can bevisible through each of the through holes 715 in the absorbent layer 710to form viewing portals 730 through the dressing to the underlyingtissue. As described above, due to the transparency or translucency ofthe cover layer and tissue contact layer, the viewing portals 730 canpermit viewing of tissue beneath the wound dressing through the woundcover when the wound dressing is applied to a patient, for exampleenabling a clinician to assess characteristics of and changes in tissueunderlying the dressing 700. The repeating pattern of holes 725 in thetransmission layer may or may not extend under the port 735 in variousembodiments. As described above, some or all of the through holes 725may comprise a plug material.

III. Example Materials

FIGS. 8A and 8B illustrate one embodiment of spacer layer materialsuitable for use as a transmission layer, which may be used in any ofthe dressing embodiments described above. The spacer or transmissionmaterial is preferably formed of a material having a three dimensionalstructure, and may have a top layer and a bottom layer comprising a knitpattern. For example, a knitted or woven spacer fabric (for exampleBaltex 7970 weft knitted polyester) or a non-woven fabric could be used.The top and bottom fabric layers may comprise polyester, such as 84/144textured polyester or a flat denier polyester. Other materials and otherlinear mass densities of fiber could of course be used. In someembodiments, the top and bottom fabric layers may be the same patternand the same material, and in other embodiments they may be differentpatterns and/or different materials. The top fabric layer may have morefilaments in a yarn used to form it than the number of filaments makingup the yarn used to form the bottom fabric layer, in order to controlmoisture flow across the transmission layer. Particularly, by having afilament count greater in the top layer, that is to say, the top layeris made from a yarn having more filaments than the yarn used in thebottom layer, liquid tends to be wicked along the top layer more thanthe bottom layer. FIG. 8A illustrates one possible knit pattern for atop or bottom fabric layer.

As illustrated in the side view of FIG. 8B, between the top and bottomfabric layers may be a plurality of filaments. The filaments maycomprise a monofilament fiber or a multistrand fiber, and may be knittedpolyester viscose or cellulose. In some embodiments, a majority of thefilaments, by volume, may extend vertically (that is, perpendicular tothe plane of the top and bottom layers), or substantially or generallyvertically. In another embodiment, 80%-90% (or approximately 80% toapproximately 90%) of the filaments or more, by volume, may extendvertically, or substantially or generally vertically. In anotherembodiment, all or substantially all of the filaments, by volume, mayextend vertically, or substantially or generally vertically. In someembodiments, a majority, 80%-90% (or approximately 80% to approximately90%) of the filaments or more, or even all or substantially all of thefilaments, extend upward from the bottom fabric layer and/or downwardfrom the top fabric layer, and in some embodiments, such filamentsextend over a length more than half the distance between the top andbottom fabric layers. In some embodiments, a majority, 80%-90% (orapproximately 80% to approximately 90%) of the filaments or more, oreven all or substantially all of the filaments, span a distance that isgreater in a direction perpendicular to the top and bottom fabric layers(a vertical direction) than in a direction parallel to the top andbottom fabric layers (a horizontal direction). The orientation of suchfilaments may promote vertical wicking of fluid through the spacerlayer. In some embodiments, the ratio of the amount of fluid wickedvertically through the spacer material to the amount of fluid wickedlaterally across the spacer material when under negative pressure may be2:1 or more, or approximately 2:1 or more, or may be up to 10:1 or more,or approximately 10:1 or more, in some embodiments. Such filaments mayalso keep the top and bottom layers spaced apart when exposed tocompressive forces or negative pressure.

FIGS. 9A and 9B illustrate one embodiment of acquisition distributionlayer material which may be suitable for use as a transmission layer inany of the dressing embodiments described above. To those versed in theart of acquisition distribution layers it would be obvious that otherADL materials may be used to achieve a similar effect. Such ADL layersmay be composed of multiple fibre types and be complex in structure anddesign. The ADL material, in an uncompressed state, may be 0.1 mm to 4mm thick, or approximately 0.1 mm to approximately 4 mm thick, and insome embodiments may be 1.2 mm thick, or approximately 1.2 mm thick, inan uncompressed state. The ADL material may comprise a plurality ofloosely packed fibers, which may be arranged in a substantiallyhorizontal fibrous network.

In some embodiments, the ADL material may consist of a mix of two fibertypes. One may be a flat fiber which may be 20 μm to 50 μm in width, orapproximately 20

μm to approximately 50 μm in width, and may comprise a cellulosic basedmaterial. The other fiber may be a two component fiber that has an innercore that is 8 μm to 10 μm in diameter, or approximately is 8 μm toapproximately 10 μm in diameter, and an outer layer with a thickness of1 μm to 2 μm, or approximately 1 μm to approximately 2μm. The twocomponent fiber may be a mix of a polyethylene (PE) type material, andpolyethylene terephthalate (PET). In some embodiments the inner core ofthe two component fiber may be PET and the outer layer may be PE. ThePE/PET fibers may have a smooth surface morphology, while the cellulosicfibers may have a relatively rougher surface morphology. In someembodiments the ADL material may comprise about 60% to about 90%cellulosic fibers, for example approximately 75% cellulosic fibers, andmay comprise about 10% to about 40% PE/PET fibers, for exampleapproximately 25% PE/PET fibers.

FIG. 9A illustrates a backscatter scanning electron microscope (SEM)plan view of a sample portion of acquisition distribution layer materialat 140× magnification. FIG. 9B illustrates an SEM cross sectional viewat 250× magnification. As illustrated in FIG. 9B, a majority of thefiber volume may extend horizontally (that is, parallel to the plane ofthe top and bottom surfaces of the material), or substantially orgenerally horizontally. In another embodiment, 80%-90% (or approximately80% to approximately 90%) or more of the fiber volume may extendhorizontally, or substantially or generally horizontally. In anotherembodiment, all or substantially all of the fiber volume may extendhorizontally, or substantially or generally horizontally. In someembodiments, a majority, 80%-90% (or approximately 80% to approximately90%) of the fibers or more, or even all or substantially all of thefibers, span a distance perpendicular to the thickness of the ADLmaterial (a horizontal or lateral distance) that is greater than thethickness of the ADL material. In some embodiments, the horizontal orlateral distance spanned by such fibers is 2 times (or about 2 times) ormore, 3 times (or about 3 times) or more, 4 times (or about 4 times) ormore, 5 times (or about 5 times) or more, or 10 times (or about 10times) or more the thickness of the ADL material. The orientation ofsuch fibers may promote lateral wicking of fluid through the ADLmaterial. This may more evenly distribute fluid such as wound exudatethroughout the ADL material. In some embodiments, the ratio of theamount of fluid wicked laterally across the ADL material to the amountof fluid wicked vertically through the ADL material under negativepressure may be 2:1 or more, or approximately 2:1 or more, or may be upto 10:1 or more, or approximately 10:1 or more, in some embodiments.

FIGS. 10A and 10B illustrate one embodiment of absorbent layer materialwhich may be used in any of the dressing embodiments described above.FIG. 10A illustrates a three dimensional microtomographic crosssectional view of a sample of absorbent material, depicting a fibrouscomposition interspersed with superabsorbent particles.

FIG. 10B is a cross sectional schematic diagram of an embodiment of theabsorbent material illustrating a plurality of layers within theabsorbent material. The absorbent material may have a textured layer4210 on one side of a fibrous network, the fibrous network defining thebulk of the absorbent material and comprising layers 4220, 4240, and4250. Superabsorbent particles 4230 may be dispersed throughout layers4220, 4240, and 4250. The textured layer 4210, also referred to as the“tissue dispersant layer” in above portions of this specification, maybe configured to laterally transmit fluid. Though depicted as thelowermost layer of the absorbent material, the textured layer 4210 mayin some embodiments be positioned as the uppermost layer of theabsorbent material, and in some embodiments may be positioned as boththe lowermost and uppermost layers of the absorbent material. Thetextured layer 4210 may comprise flat fibers 20 μm to 50 μm in width, orapproximately 20 μm to approximately 50 μm in width. The textured layer4210 may comprise 1 to 2 or approximately 1 to approximately 2 layers ofthe flat fibers, and the textured layer 4210 may have an overallthickness of 0.04 mm, or approximately 0.04 mm.

The bulk of the absorbent material, comprising layers 4220, 4240, and4250, may have a thickness of 1.7 mm, or approximately 1.7 mm, or mayhave a thickness in the range of 0.5 mm to 5.0 mm, or about 0.5 mm toabout 5.0 mm. The bulk of the absorbent material may comprise a mix oftwo fiber types arranged in a fibrous network, for example thecellulosic fiber having a width of 20 μm to 50 μm, or approximately 20μm to approximately 50 μm, and the PE/PET composite fiber, describedabove with respect to the ADL material. The superabsorbent particles4230 may be irregularly shaped and varied in size, and may have adiameter of up to 1 mm, or approximately 1 mm. The superabsorbentparticles 4230 may comprise a sodium acrylate type material. There maybe relatively fewer superabsorbent particles in a portion of theuppermost surface of the bulk of the absorbent material (the surface oflayer 4250 opposite the textured layer 4210), for example in anuppermost surface having a thickness of approximately 0.1 mm.

Layer 4220 may be a liquid absorption layer configured to draw liquidupward through the material towards layers 4240 and 4250. Layer 4240 maybe a storage layer configured to hold absorbed liquid. Layer 4220 may bea liquid distribution layer configured to apply a “reverse suction”effect to the liquid storage layer 4240 in order to inhibit (orsubstantially inhibit) absorbed liquid from leaking back down throughthe lower layers of the absorbent material, a phenomenon which iscommonly known as “back wetting.”

Superabsorbent particles 4230 may be distributed primarily within thestorage layer, may extend partially into the absorption layer 4220 andliquid distribution layer 4250, or may be distributed evenly (orsubstantially evenly) throughout the layers. The layers 4220, 4240, and4250 may overlap with a portion of adjacent layers, and may or may notbe separable.

FIG. 11 illustrates one embodiment of an adhesive spread onapproximately one square centimeter of a film material, which may beused as the cover or backing layer in any of the dressing embodimentsdescribed above. The adhesive on the film has been covered with carbonpowder for ease of illustrating the spread of the adhesive. The adhesivemay comprise, for example, an acrylate type adhesive, for example K5adhesive, and may be laid down in a criss cross pattern. In someembodiments, the adhesive material may cover approximately45.5%±approximately 1.3% of the film surface. The pattern and coverageof the adhesive may vary so long as the configuration is suitable fordesired vapor permeability.

IV. Example Dressings with Plug Material

FIGS. 12A-12E are photographic representations of various embodiments ofa wound dressing configured for enhanced tissue visibility through plugmaterial. As described above, the plug material can be any soft,transparent or translucent, and optionally hydrophobic material, withone example being silicone. Plug material can be positioned within someor all through holes in the dressing.

FIG. 12A illustrates one embodiment of a wound dressing having at leastone internal layer positioned between a cover layer and a wound contactlayer having a sealed perimeter, the at least one internal layer havinga first through hole positioned so as to underlie a suction port (notattached in this illustration) and a viewing window matrix of additionalthrough holes windows through the dressing. In this embodiment, eachhole in the viewing window matrix is provided with a pillar of plugmaterial. The through hole to underlie the suction port may not beprovided with plug material. In certain embodiments, the at least oneinternal layer includes two or more layers (e.g., a transmission layerand an absorbent layer over the transmission layer), and the pillar ofplug material can extend fully through both of the layers. In someembodiments, the through holes of the transmission layer and theabsorbent layer may have the same dimension or diameter. In otherimplementations, the pillar of plug material can extend through just onelayer, or at least partially through one or more layers. The pillars ofplug material can have a diameter of 10 mm (or approximately 10 mm) insome examples.

FIG. 12B illustrates another embodiment of a wound dressing having atleast one internal layer with a viewing window matrix having the throughholes filled with pillars of plug material. The embodiment of FIG. 12Bincludes a flexible suction adapter attached to the cover layer of thedressing over the first through hole. FIG. 12C illustrates theembodiment of FIG. 12B with the suction adapter attached to a portable,compact negative pressure pump. In other embodiments a length ofextension tubing may be coupled between the pump and the suctionadapter, and various other negative pressure pumps may be coupled to thesystem in place of the illustrated compact pump.

FIG. 12D illustrates a close-up view of a portion of the viewing windowmatrix of the embodiment of FIG. 12B, each through hole in the viewingmatrix having a pillar of plug material extending through both anabsorbent layer and a transmission layer positioned underneath theabsorbent layer. The through holes forming the viewing windows can bealigned and can have a diameter of 10 mm (or approximately 10 mm), andthe pillars of plug material can have a diameter of 10 mm (orapproximately 10 mm) in some examples.

FIG. 12E illustrates a visual example of the enhanced visibilityprovided by a dressing with viewing windows such as is described herein.The illustrated dressing is placed over a surface with a variety ofmarkings that are clearly visible through the viewing windows.Accordingly, a clinician can use such a dressing to visually assess thecondition of tissue underlying the dressing.

In an alternate embodiment, a dressing can include a transmission layerthat is transparent, translucent, or contains more open areas (e.g., aless dense weave) with holes smaller than approximately 10 mm indiameter, and the pillars may only extend through the absorbent layer.Accordingly, the transmission layer may extend underneath the pillars ofplug material in the absorbent layer, thereby providing enhancedtransmission of negative pressure and/or spread of wound exudatecompared to embodiments having plug material positioned within thetransmission layer.

In another alternate embodiment, rather than having the plug materialformed as pillars through one or more layers, a dressing may have alayer or structure of transparent or translucent material (for example,silicone) with an array of absorbent or superabsorbent materialportions. For instance, the transparent or translucent layer orstructure may form an interconnected frame extending across the lengthand width of the wound dressing, and have a matrix of holes or spaceswithin the frame where absorbent material can be provided to fill theholes or spaces. In some examples, the transparent or translucent layermay take the same shape as any of the embodiments of the absorbent layerpreviously described, and the superabsorbent material portions may takethe shape of any of the embodiments of the pillars previously described.Alternatively, a dressing may comprise alternating struts, strips orbands of transparent or translucent material and struts, strips or bandsof absorbent material. For example, a wound dressing layer may comprisediagonal alternating bands of transparent or translucent material andabsorbent material. In any of the aforementioned embodiments, atransmission layer may be provided under the transparent or translucentmaterial and the absorbent material for transmission of negativepressure, and a suction adapter or other negative pressure source may beprovided to communicate negative pressure to a wound site, optionallythrough a through hole in either the absorbent material or in thetransparent or translucent material.

V. Terminology

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example describedherein unless incompatible therewith. All of the features disclosed inthis specification (including any accompanying claims, abstract anddrawings), and/or all of the steps of any method or process sodisclosed, may be combined in any combination, except combinations whereat least some of such features and/or steps are mutually exclusive. Theprotection is not restricted to the details of any foregoingembodiments. The protection extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of protection. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms. Furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made. Those skilled in the art willappreciate that in some embodiments, the actual steps taken in theprocesses illustrated and/or disclosed may differ from those shown inthe figures. Depending on the embodiment, certain of the steps describedabove may be removed, others may be added. Furthermore, the features andattributes of the specific embodiments disclosed above may be combinedin different ways to form additional embodiments, all of which fallwithin the scope of the present disclosure.

Although the present disclosure includes certain embodiments, examplesand applications, it will be understood by those skilled in the art thatthe present disclosure extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses and obviousmodifications and equivalents thereof, including embodiments which donot provide all of the features and advantages set forth herein.Accordingly, the scope of the present disclosure is not intended to belimited by the specific disclosures of preferred embodiments herein, andmay be defined by claims as presented herein or as presented in thefuture.

1-54. (canceled)
 55. A wound dressing comprising: a material layer; aplurality of plug materials extending vertically through a thickness ofthe material layer; and a cover layer positioned above the materiallayer, the cover layer configured to form a negative pressure chamberunderneath the cover layer, the cover layer couplable to a source ofnegative pressure configured to create negative pressure in the negativepressure chamber.
 56. The wound dressing of claim 55, further comprisinga port configured to communicate negative pressure to the negativepressure chamber.
 57. The wound dressing of claim 56, wherein the portis configured to be attached to the cover layer.
 58. The wound dressingof claim 55, wherein the material layer comprises a foam.
 59. The wounddressing of claim 55, wherein the cover layer is transparent ortranslucent.
 60. The wound dressing of claim 55, wherein the materiallayer comprises a plurality of through holes extending verticallythrough the thickness of the material layer, wherein the plug materialsare positioned within at least some of the plurality of through holes.61. The wound dressing of claim 60, wherein the through holes areconfigured to permit viewing of tissue beneath the wound dressingthrough the cover layer when the wound dressing is applied to a patient.62. The wound dressing of claim 55, wherein the plug materials arecylindrical.
 63. A method of treating a wound, the method comprising:applying a wound dressing to the wound, the wound dressing comprising: amaterial layer; a plurality of plug materials extending verticallythrough a thickness of the material layer; and a cover layer positionedabove the material layer, the cover layer configured to form a negativepressure chamber underneath the cover layer, the cover layer couplableto a source of negative pressure configured to create negative pressurein the negative pressure chamber.
 64. The method of claim 63, whereinthe wound dressing further comprises a port configured to communicatenegative pressure to the negative pressure chamber.
 65. The method ofclaim 64, wherein the port is configured to be attached to the coverlayer.
 66. The method of claim 63, wherein the material layer comprisesa foam.
 67. The method of claim 63, wherein the cover layer istransparent or translucent.
 68. The method of claim 63, wherein thematerial layer comprises a plurality of through holes extendingvertically through the thickness of the material layer, wherein the plugmaterials are positioned within at least some of the plurality ofthrough holes.
 69. The method of claim 68, further comprisingvisualizing tissue beneath the wound dressing through the cover layerthrough the through holes.
 70. The method of claim 63, wherein the plugmaterials are cylindrical.
 71. A dressing, comprising: a foam layer; aplurality of cores extending substantially through the foam layer; and adrape sealable over the foam layer and a wound bed, the drape defining asubstantially-airtight volume between the drape and the wound bed thatcontains the foam layer, the drape couplable to a pump operable tocreate a negative pressure in the substantially-airtight volume.